The present invention relates to a one-way clutch including a pair of input/output members coaxially combined with each other for transmitting torque in a specified direction inputted to one of the input/output members to the other and not transmitting torque in the opposite direction inputted to one of the input/output members to the other. More particularly, it relates to the development of a low-cost one-way clutch of simple structure which need not operate with high precision.
As typical one-way clutches for use in automobiles, agricultural machinery, OA equipment, and the like, there have been known a sprag one-way clutch using a top in the form of a cocoon and a roller one-way clutch. By way of example, a description will be given to a roller one-way clutch as a conventional one-way clutch. As shown in FIG. 9, the roller one-way clutch comprises: an inner race a; and an outer race b combined with the inner race a so that it can rotate relative thereto; a plurality of recessed portions c (only one recessed portion is shown) formed circumferentially in the inner surface of the outer race b with given regular pitches; rollers d positioned in the respective recessed portions c; and springs (not shown) for biasing the individual rollers d disposed in the corresponding recessed portion c in such a direction (counterclockwise) that the roller is pushed into the space between the outer surface e of the inner race a and the inner surface f of the outer race b.
When torque in the direction (clockwise) opposite to the biasing direction of the spring is inputted to the inner race a, the rollers d are not caught in the spaces between the inner and outer races a and b so that the inner race a rotates freely from the outer race b. Consequently, the torque inputted to the inner race a is not transmitted to the outer race b and hence the outer race b does not rotate. When torque in the same direction (counterclockwise) as the biasing direction is inputted, the rollers d are caught in the spaces between the inner race a and the outer race b to exert a wedging action whereby the inner and outer races a and b are locked. Consequently, the torque inputted to the inner race a is transmitted to the outer race b so that the outer race b rotates in the same direction as the inner race a.
However, it is difficult to implement the conventional one-way clutch at low cost since it requires high-precision components and has a complicated structure.
When the torque inputted to the inner race a is excessively large over the maximum torque that can be transmitted by the clutch, the clutch will be broken. In case of breakage, replacement of the broken components is not sufficient and the whole one-way clutch should be replaced by a new one. To avoid the situation, it is necessary to preliminarily provide the one-way clutch with an additional torque limiter, which further increases cost.
Since the maximum transmissible torque cannot be changed in the conventional one-way clutch, the excessively large torque inputted to the inner race a is outputted as it is from the outer race b provided that the torque is smaller than the maximum transmissible torque. In this case also, the torque limiter is required to prevent the situation.
The present invention has been achieved in view of the foregoing circumstances. It is therefore an object of the present invention to provide a low-cost one-way clutch of simple structure utilizing belt transmission mechanism between two axes. The one-way clutch need not operate with high precision and suffers only a reduced number of failures resulting from excessively large input torque. In the event of failure, it is sufficient to replace only the failed component of the one-way clutch. Moreover, the maximum transmissible torque can be varied in the one-way clutch.